PROJECT SUMMARY National data indicate over 650,000 children and adolescents are exposed to physical, sexual, or emotional abuse or physical or emotional neglect each year. Moreover, youth with a history of childhood maltreatment (CM) are at least twice as likely to develop depression and are at substantial risk for non- response to current best practice depression interventions (i.e., cognitive behavioral therapy and antidepressants) compared to non-maltreated peers. Research suggests that CM increases risk for depression through disruptions in the positive valence system, such as reward processing, and Behavioral Activation (BA) may be an alternative depression intervention that targets these deficits. This proposal takes an innovative approach integrating neural, behavioral, and novel mobile technologies to measure longitudinal change in reward processing as a mechanism of BA intervention response among depressed adolescents with a history of CM. This proposed K23 bridges the candidate's prior training in environmental, biological, and affective etiological processes contributing to adolescent depression with new training in 1) target-focused intervention research, 2) developmental affective neuroscience, and 3) technology-based assessment tools. This training will uniquely position the candidate to investigate biomarkers of intervention response across multiple levels of analysis, with an emphasis on vulnerable youth at risk for intervention non-response. Specifically, depressed adolescents with a history of CM will complete pre- and post- BA intervention fMRI and behavioral measures of reward processing along with daily passive mobile monitoring of physical (steps) and social (amount of texts, calls, social media usage) activity to determine 1) how BA targets neural and behavioral reward processing and real-world behavioral engagement (Specific Aim 1), and 2) whether change in neural and behavioral reward processing predicts intervention response and maintenance (Specific Aim 2). To achieve these research and training goals, the candidate will receive training from an ideal mentorship team within an optimal scientific training environment. Dr. McCauley is an expert in the etiology and treatment of adolescent depression and developed a BA protocol targeting the increase of rewarding experiences and decrease of avoidance specific to adolescents. Dr. McLaughlin has significant expertise in developmental affective neuroscience and the use of fMRI methodology to study neural circuitry related to affective and reward processing among youth exposed to maltreatment. Dr. Aren provides additional expertise in target-focused depression intervention research as well as extensive experience in the use of mobile technologies to assess real-time behavior, affect, and mental health. Training and research activities will prepare the candidate to achieve the career objective of developing a larger program of research contributing to Objective 3 of NIMH Strategic Research Priorities by investigating innovative biomarkers of intervention response in an effort to tailor interventions and optimize outcomes in vulnerable populations.